AP PhotoInternal Revenue Service (IRS) Commissioner Douglas Shulman testifies on Capitol Hill in Washington, Thursday, Aug. 2, 2012, before the House Oversight Committee. Investigators say the IRS may have delivered more than $5 billion in refund checks to identity thieves who filed fraudulent tax returns for 2011.

A report released by the U.S. Treasury Inspector General for Tax Administration reveals rampant tax fraud in the federal government's Individual Taxpayer Identification Number (ITIN) program, including the discovery of one Atlanta address which received $46.3 million in fraudulent tax returns.

In its report, the Treasury's inspector general accused the Internal Revenue Service of discouraging its employees from rooting out fraud in the program that assigns taxpayer-ID numbers to non-U.S. residents and others who don't qualify for a Social Security number, The Wall Street Journal said. The management failures, which were likely a way to speed up processing, can lead to the creation of fictitious identities and result in fraudulent tax returns.

Specifically, the report said there were 154 mailing addresses that were used 1,000 or more times on ITIN applications in the 2011 processing year. One Phoenix address was assigned 15,795 numbers, Fox News reports.

The inspector general found that 10 individual addresses were used for filing 53,994 tax returns and receiving $86.4 million in fraudulent refunds. The single address with the highest reported refund total was in Atlanta, where 23,994 tax returns totaled $46.3 million in refunds.

Additionally, Fox News said that reports also found that 10 bank accounts received 23,560 tax refunds totaling more than $6 million. One account received 2,706 tax refunds worth $7.3 million.

Treasury Department investigators estimated last week that the IRS may have delivered more than $5 billion in refund checks to identity thieves who filed fraudulent tax returns in 2011, according to USA Today. IRS Commissioner Douglas Shulman testified on Capitol Hill before the House Oversight Committee on Aug. 2 to address the fraud.

The IRS issued a statement recognizing the problems with the ITIN process and announcing that top officials have "moved quickly and aggressively" to address the issues.

"We have already taken major steps to strengthen our documentation standards required in order to obtain an ITIN, and we have significantly increased our scrutiny of applications," the letter also stated, according to Fox News. "In addition, the IRS has obtained new tools and equipment to help employees improve their ability to detect fraudulent documents."